Fuel cells combine hydrogen and oxygen without combustion to form water and to produce direct current electric power. The process can be described as electrolysis in reverse. Fuel cells have been pursued as a source of power for transportation because of their high energy efficiency (unmatched by heat engine cycles), their potential for fuel flexibility, and their extremely low emissions. Fuel cells have potential for stationary and vehicular power applications; however, the commercial viability of fuel cells for power generation in stationary and transportation applications depends upon solving a number of manufacturing, cost, and durability problems.
The most promising fuel cells for widespread transportation use are Proton Exchange Membrane (PEM) fuel cells. PEM fuel cells operate at low temperatures, produce fast transient response, and have relatively high energy density compared to other fuel cell technologies. Any fuel cell design must: (a) allow for supply of the reactants (typically hydrogen and oxygen); (b) allow for mass transport of product (water) and inert gases (nitrogen and carbon dioxide from air), and (c) provide electrodes to support catalyst, collect electrical charge, and dissipate heat. Electrical and thermal resistance, reactant pressures, temperatures, surface area, catalyst availability, and geometry are the main factors affecting the performance and efficiency of a fuel cell.
One problem encountered in dealing with PEM fuel cells is the need to reduce thermal and mechanical stress concentrations and to increase integrity and performance of the fuel cell. Current phosphoric acid and PEM fuel cells rely on flat-plate electrodes. Flat plate PEM fuel cells suffer from reactant flow distribution problems which can cause inefficient operation and even premature failure of the fuel cell. The use of tubular, or capillary PEM fuel cells could lead to lower thermal stress and reduced manufacturing costs.
One problem with both flat plate and cylindrical fuel cells is power loss due to the resistance of the electrode and electrolyte, which increases with the required size of the fuel cell. A PEM fuel cell with a spiral wrapped configuration would minimize electrical resistance losses, while permitting scale-up of the fuel cell to larger sizes without unduly increasing the resistance of the electrode and electrolyte. A spiral wrapped fuel cell could be increased in size simply by adding more spiral wraps without unduly increasing the distance over which the electrical current must be collected.
Simple methods are needed to manufacture spiral wrapped PEM fuel cells, contained in a cylindrical chamber.